Variable pitch airplane propeller



VARIABLE PITCH AIRPLANE PROPELLER Jug 24, 1939.

Filed Dec. 7, 1935 9 Sheets-Sheet l ATTORNEYS Jan. 24, 1939. P. G. A. LEvAssEUR VARIABLE FITCH AIRPLANE PROPELLER 9 sheets-sheet 2 Filed Dec. 7, 1935 INvENToR ATTORNEYS Jan.24,.1939. BGA. LEVASSEUR `2,144,927'

VARIABLE PITCH AIRPLANE PROPELLER Filed Deo. 7, 1935 9 Sheets-Sheet INvENToR' z/rf @vigas ZIM/ Lez/awful RYLUU mand ATTORNEYS Jan. 24, 1939. P, G. A, LEVASQSEUR 2,144,927

VARIABLE PITGH AIRPLANE PROPELLER 'Filed Dec. 7, 1935. 9 Sheets-Sheet 4 l N vENroR P401? wfgfes ler/ Masseur BVM ATTORNEYS Jan 24, 1939- P. G. A. Lx-:vAssEUR 2,144,927 VARIABLE FITCH AIRPLANE PROPELLER 9 Sheets-Sheet 5 Filed Deo. '7, 1955 3)/ ffl/14 Jan. 24, 1939.l P. G. A. LEvAssl-:UR 2,144,927

VARIABLE PITCH AIRPLANE PROPELLER Eff/a Filed DBC. 7,- 1935 9 Sheets-Sheetl 6 44' lvm/Tale Plkns @songes A LBERT El/Assem ATTaRNEvs P. G. A. LEVASSEUR l VARIABLE FITCH AIRPLANE PROPELLER Jan, 24, 1939.

Filed Deo. 7, 1935 9 Sheets-Sheet 7 INVENTOR Jan. 24, 1939. F'. G. A'. I EvAssEUR 2,144,927

VARIABLE PITCH AIRPLANE PROPELLER Filed Deo. 7, 1955 9 Sheets-Sheet 8 Jan. 24, 1939. p. G. A. LEvAssL-:QR 2,144,927

VARIABLE PITCH AIRPLANE PROPELLER Filed-Dec. 7, 1955 9 sheets-sheet 9 5y dan!! Patented Jas. 24', 1939 -2,144,927 VARIABLE FITCH AIBPLANE PBLOPFILER Pierre Georges Albert Levasseur, Paris, France Application December 7, 1935, 4Serial No. 53,312

In France March 9, 1935 9 Claim. (C1- 170-163) The present invention relates to a propeller in which each of the blades can assume at least two diierent positions relative to the hub portion and if desirable, intermediate Ipositions' therebetween, it being understood that for each position Vassumedby the blades a different propeller pitch results.l

According to my invention, the blades of the propeller are mounted on the hub in such fashion i that centrifugal force always tends to return them automatically to one of two extreme'posi- 'tions, for example, the position of smallest pitch. The other of its two extreme positions, for exam- I. ple, the position of greatest pitch; may be so designed that the blades lockV in such'position by means of any suitable locking device and when initially placed in such position of greatest pitch a release of the locking means during a rotation of the propeller in ilight will result in an instant return of the propeller blades to the position of smallest pitch through the action of centriiugal force. 1f, on the other hand, suitable stops have been actuated, the blades can be caused to assume any desired intermediate position through the operation of centrifugal force and maintainsuch intermediate position until vfurther released.

The movement of the blades in the opposite direction against the action of centrifugal force is accomplished after preferably reducing the speed of the motor by means of a control mechis-had to the attached 46 trating4 one practical anism which in-turn derives its energy from the actual energy of the moving blades.

The invention relates, in addition to a method ai oi'controlling the pitch of propeller blades, to the structure for accomplishing such control which is characterized by great simplicity and ydependability in operation. Other characteristics and advantages of the invention will become apparent from the following-description, taken in conjunction with the accompnyin drawings, which show one embodiment of the invention.

With these and other objects in mind, reference sheets of drawings illusembodiment of the linvention, and, in which Fig. 1 is a perspective view of a propeller -emone form of'my invention; Y Fig. 2 is a side elevation of the propeller shown ,nllged Fig. 3 is an side elevation of the propeller hub shown inthe preceding views and illus'-, hated partially in cross-section to disclose the orf mounting of one of the blades of the Fig. 4 is a further side elevation taken along the lines IV--IV of the propeller hub illustrated in Fig. 3 and showing a further cross-section of one of the blade socket mountings;

' Fig. 5 is a plan View taken from the top of the propeller hub illustrated in Figs. l Aand 2;

Fig. 6 shows a constructional detail in section taken'along the. lines VL-VI of Fig., 5;

' Fig. 'l is a diagram showingl the developmentv of the control-cam which formsa part 'of my invention; y

Fig;8 is a side elevation par'tially in section of a propeller hub embcdyingrmy invention;

Fig. 9 is acorresponding plan view in crosssection along the lines IX-IX of Fig. 8;

Figs. 10 to l2 are a diagrammatic representation of the propeller in three pitch positions;

Fig. 13 is a. side elevation of the propeller hub embodying the invention partially broken away to show certain details of construction;

Figs. 14 to 15 show diagrammatically a' modication in construction of the propeller;

Fig. 16 is a side elevation in partial cross-section of a propeller hub showing a modified form of my invention;

Fig. 17 is a diagrammatic representation of` the modified type of structure illustrated in Fig. 16 showing -variousppitch positions of the propeller blade.

In Figs. 1 to 'l there is shown a propeller havl ing two blades, I and la, it being understood that the invention ls applicable under the same condition to a propeller having any number ci blades.

Each of the blades of the propeller is mounted under identical conditions and embodies the same structure and-under those circumstances the invention will be described with reference to one of the blades only, for example, blade I. This blade is internally screw-threaded at its inner end, (as shown at 5) to cooperate with a threaded bearing 2 formed on the hub collar 3, which in turn is flxedly mounted on the propeller shaft l. Thepitch and cross-section of the internal screw'threads 5 in the propeller blade are lsuch that under the action of the centrifugal force acting or the blades during flight the blade l tendsto unscrew itself with respect to its hub. It is, of course, apparent that by means of a screwing or unscrewing movement. of the blade.

its pitch with respect to its hub can be varied from a position of great pitch to one oi small collar in Aaddition also carries a bracket I 0,

turn tends to screw .said blade up again on its.

through which is fixed a stem-I I, of a forked member I2, the latter carrying a roller I3, which with the-cam` surface of the cam -1.

The 'details of construction, and the relative positions of said roller and its forked member with relation-to the mechanism as Ia whole, are shown in Figs. 1 through 5.4 Fig. 6 shows in cross-section the component parts of said roller assembly. The action of centrifugal force, which in the case of my invention constantly tends to unscrew the-propeller blade during rotation of' the latter, is partially compensated for by the action of a suitable retracting means, which in In the embodiment here illustrated, the retractin g means has an elastic cord I4 which is secured at one of itsends tosaid collar-8 by means of engagement with the stem I I, ofthe fork- I2, and at its opposite-end to a bracket or supporting member I5',carried by the propellerhub. ,As illustrated, the elastic cord may be secured to the bracket I5 through the medium of a pin I6, which passes through one end of said elastic cord.

Inoperation, the plate 6 normally rotates'freely with the hub-3 without any relative displacement with respect to the latter. Such a relative move-- ment can, however, .be set up and the pitch of the blades controlled by effecting a braking action on said plate 6,` by Vmeans of any well known type of brake, as for example, the internal shoe friction brake 40 as shown in Figs.. 8 and'9.

The movement of the plate 6, relative to the hub 3, is limited in both directions by the stops I1 and IB carried by the hub, and cooperating With the stop. I9, carried by the plate, as shown in Figs. 2 and14. In addition, a suitable retracting means, such as a further elastic cord 20, constantl'ytends to bring the plate 6 back into the position shown' in Fig. 5 (which is the position of greatest pitch), and inwhich the projection I1, keys against the stop I9. 'I'he elastic cord 20, is secured at one end to a pin 26, carried by the collar 8, and at its other end by a pin 21, carried by the plate 6. In use, the above described propeller functions asfollowsz It will be assumed in the rst place that the blade I l's in the position of greatest pitch, which,

Y forv example, might be the blade screwed home on the hub portion 2. yIn this position, the plate takes the position shown in Figs. 2 and 5 and the stop I 9 is in contact withthe stop I1.l In this position, the roller AI3 is in Contact with the bearing surface A of the collar 1 (see Fig. '7). When it is desired" to bring the blade into the position l of smallest pitch, a. brake 40 (see Fig.9) is ap- -at the desired position.

V placement, the roller I3 continuing meanwhileto n roller I3 reaches position D on the cam 1 (see is pivotally secured therein, and which cooperates tion on the cam 1, the stop I9 is engaged by the stop I8, and the 'plate 6 ceases to move further. Thereafter, by a release of the brake through the action of the spring or elastic 20, plate 6 is returned to its initial position, that is to say, with the roller I3 engaging the A portion of the cam 1. During the return movement just described, the roller I3 willnot follow the cam path through its B and C positions, due to the action of the elastic cord I4, which counterbalancing the action of centrifugal force, holds the roller I3 for the short space of time during which the return movement takes place along a substantially rectilinear course as shown bythe dotted line 2I in'Fig. 7. Thus,

the change from position of least pitch to the position -of greatest pitch has been effected by simply braking the movement of the plate B after first reducing the speed of rotation of the propeller shaft and thus lessening the action of centrifugal force.

The movements of the blades of the propeller, regardless of their number, may be rendered simultaneous through the use, for example,.of a connecting collar 22 provided in turn with a trunnion 23 for each of the blades. On said trunnionA is mounted a link 24, which is in turn carried by a further trunnion. 25, secured to the collar 8. Thus, movement of the collar 8, as the blade I rotates, carries with it through the coupling link mechanism the collar 22 which, in turn, actuates each of the remaining blades through its corresponding link structure.

As just described, the` blades of the propeller' may be brought into two extreme positions, those of greatest and least pitch, respectively.

In Figs. 8 through l2 the device illustrated enables the blades to be heldin addition in intermediate positions. 'Ihis is accomplished by providing a braking device for holding the plate 6 For example, a brake shoe 4I, carried by a rocking arm 42, pivotally secured as at 42A, to the sleeve 43, encircling the propeller shaft, may be provided.. Looking at Fig. 9, we note' that the rocking arm 42 is not arranged along a radius of the propeller shaft and thus the movement of the plate 6, relative to the sleeve 43, can always take place freely in the direction of the arrow F, Whereas, movement in the direction of the arrow F can only take place when the brake shoe 4I has been backed away from engagement with the plate 6. Such latter movement can be effected by means, for example, of an additional brake memberv 44, cooperating with a crown 45 secured to the arm 42. Inasmuch asthe arm V42 rotates withsa continuous movement, together with the sleeve 43 and the shoe 4I a slight braking action on the ciiwn will obtain a rocking movement of the lever about the pin 42A carrying the brake sho'e 4I away from the' 10 the plate B yis shown in th position in which 1 the roller I3 is in contact with the lowest portion of the cam 1, at which time' the .blade is in its position of greatest pitch. Brakes 4II and .44. are in released position at this point. When the pilot wishes to reduce the pitch, he applies thel brake 4II a'gaii'istl the plateV 6. A relative displacement .takes place coincident with such braking between the plate 6 and the shaft 4, asa consequence of -whichthe roller I3 proceeds along the cam surface to the position indicated in Fig. -11. Thish causes the plate to vassume its position of least pitch. It will be understood, in this connection, that when the parts have assumed the shown in- Fig. 11, they areimmediately locked in position so that position the action of the centrifugal force will not return the blade to its greatest pitch position. A I3 exerts a continuous downward the cam surface 1 which tends to move the`.cam and ring to the right or in the direction of the horizontal arrow-in Fig. 11. However, Ythe movement of the cam and plate 6 is prevented y engaging it with the brake shoe '4I which locks the parts in position. Consequently, as is shown in Fig. 12, the pilot may cause the blades of the propeller to assume a position betwen the positions of extreme pitch by manipue lating the brake shoes 4I and 44. For example,

-application of the brake shoe 44 automatically `causes a release of the brake shoe 4I and, at the Isame time, brings the roller I3 down the cam 'Position A, .as shown in pdsition of least pitch and surface 1 through-rotation of the latter, for example, to the position occupied in Fig. 12. If desired, the movement of the plate 6 can be facilitated by use of a spring 45 and, in addition, stops 50, as shown in Fig. 9 secured to the sleeve 43, will limit the movement of the plate in bothpdirections by cooperating with the projection I, carried by the plate 5. F A

' In Figs. 13 through 15, there 'is illustrated a modified form of invention.` In these views, the cam surface is provided yviththree steppedpositions which may be -assumed by the roller I3. Figs. 14 and 15, is the position B is the position of greatest pitch, while the intermediate posi- Vtion is shown at E.

It will be noted that a bolt 41, having a rounded end portion 41a, is positioned in a recess-formed in the cam surface 1 at A and a coil spring 49 is likewise positioned in saidV recess and tends normally to lift said bolt upwardly abovethe surface of said cam. A stop 4l is positioned beneath said cam and may be secured to a sleeve encircling the propeller shaft. 'I'his stop engages the end of the bolt 41 at 41a when the roller I3 is about to assume the position E on the cam. When the miler Il is at rest in the E position, the spring 49 liftsthe bolt upwardly above the surface of the cam thus retracting the end portion 41a from ensagement with the stop 4I, Vand allowing further l'15pacientes!lurmemsut the bolt 41" comes into contact iwiththe stop 48- befetheformrhashadanopportunitytobe the spring 4I.` Sidewlse action,

cient to hold th Aparte m that position against the action of the spring 4l, therefore, as long as brakihgaction is' maintained causing the dis-'1 placement ofthe cam 1, 'the' bolt 41 will remain in contact with the stop 44. and .resistjdisplace ment.

In operation, when the -pnot reels me bou l1 contact the stop 48, he should immediately release the brake 4Iwhich will allow the spring 49 to project .the bolt 41 into inoperative position and out of contact with the stop 4I.. At this time, the roller I3, which is still firmly pressed against the .camsurface 1, will itself act on the inclined portion of the intermediate surface E to displace cam 1 in the same direction and bring it in the first position as shownby the dotted lines in'Fig. u..

In other 'words,`in moving from position A to position E a second stage movement occurs. The first stage embraces the pilot, exerting braking which brings the cam surface 1 to a position at which the finger 41 firmly engages the -stop 48. The second stage occurs, when the pilot discontinues the braking action and the roller I3 actsto continue the displacement of plate 1 to bring it to position 1.

In Fig. 15 is illustrated the same type of structure, which in this instance enables the plate to be locked in four distinct positions, for which purpose, a second locking member, like bolt 41, is provided. Figs. 16 and 17 illustrate a structural modification of my device as applied, for example, to a three bladed propeller. In this form of the invention, the springs or elastic cords are replaced by a single coil spring 50a, mounted, for example, in a casing 5Ia inv the'hub axis. Said spring is secured at its outer end to the hub, and at its inner end to a bevelled pinion 52, which,'in turn, meshes vwith a gear member 54 locatedrbelow the gear 52 on the same shaft with a further pinion -gear 55, which, in turn, cooperates with a tooth segment 56 secured to the hub of the propeller blade. It will thus be obvious, that a force set up in the*l coil spring 50a, acting through the gear train, will eect a rotation of the propeller blades. The arrangement is similar to the part played by the spring or elastic members I4, in the device heretofore described, in connection with Figs. 1 through '1. However, in this modication, the limitation placed on the angular .displacement of the blades, could be greater than in the modification heretofore described.

In Fig. 17, for example, the" propeller blade I has beenv shown in full lines' in the high pitch position, but by means of the mechanism just described could be brought at will to the position of least pitch, as shown bythe dotted lines Ia. If, forany reason, the propeller shaft should cease rotating, the blades could in turn assume the position shown on the dotted lines Ib, at which point, they oi'fer the least resistance toforward motion of the plane. It is also obviouathatthe con spring arrangement lends itself to use in propeller structures of this type, regardless, of whether or not,itisdesiredtopermitthebladestobe brought into the position of least resktance.

It will be apparent that mm changes can be madeinthesh'uctureandgn'ofmydevlce,

fof the inventionV contained I claim:

tllul'hich-nbe the plate to limit the `movements of the saine with reference to said shaft to a given zone, and between two extremev positions, cams secured to said plate and cooperating one with each of said rollers, each of said cams including a proiecting` fiat portion against which the roller bears in one of the extreme lpositions of the blade, a recess, against the bottom of which the roller bears in the other extreme position of the blade, an intermediate portion arranged between said projecting portion and said recess, a second projecting flat portion and a slope which connectsI the bottom of nrst position subsequent to the cessation of func-A tioning of said braking means.

"7. A propeller having a pitch which is variable during flight, comprising -a hub, radial bearings' securedto said hub, a blade mounted on each of said bearings for rotation about its longitudinal axis in opposite directions, in one of which the blade is constantly urged, during night, by the forces acting on it, a roller carried by each of the blades, a plate loosely mounted on the propeller shaft, means for restricting the movements of said plate with given zone and between two extreme positions, said plate presenting against which the roller is constantly pressed and y 46 along which` it tends to descend under thev action of the forces urging the blade, braking means acting on the plate to cause a relative displacement thereof during which the cam causes the displacement of the said roller against the action of the said forces, automatic locking means acting normally on the plate to prevent its movement in one direction, under the action of the rollers on the cams,

but permitting its movement in the opposite direction under the braking action, and means for 'releasing said locking means to permit the movement in the direction in which it is normally prevented. j

, 8. A variable pito bearings extending radially from said hub, rotatably mounted' by each of said bearings, said reference to said shaft to a for each roller, a cam blades tending, during rotation of said hub, to rotateincident to the forces acting thereonin one direction, a'roller carried byeach of said blades, a plate rotatable with respect to said hub and presenting inclined surfaces for each of said blades, said rollers bearing against the plate surfaces, braking means cooperativewith said plate to cause relative rotation thereof with respect to said hub whereby to cause the inclined surfaces of said plate to displace said rollers against the action of the forces normally acting on said blades, a brake shoe co-actingwith said plate in a single direction of movement of the latter with respect-to said hub, a movable drum, a brakeco-acting with said drum, and an arm connected to said drum and said brake shoe.

9. A propeller having a pitch which can be varied during flight, said propeller including a hub to be mounted on a propeller shaft, radial bearings secured to said hub, a blade mounted on each of said bearings for rotation 'in opposite directions about its axis and in one of which directions the blade is constantly urged during flight by the forces acting on it, a roller carried' by each of the blades a plate mounted on the propeller shaft, means confining the movements of said plate to a given zone between two extreme positions, cams secured to said plate and cooperating one with of said rollers, each of said cams including projecting nat portions against one of whichV the co-operating roller bears in one of the extreme positions oi the blade, a .recess against the base of which the roller bears in the other extreme position of the blade, two 'intermediate portions disposed between said projecting portion and said recess, and a cam portion which connects the bottom of said recess to the t second projecting fiat portion, acting on the plate to cause a relative displacement thereof and to successively bring the roller from its position on the rst first intermediate position, a retractible bolt for maintaining such roller in such intermediate posil tion, said roller subsequent to the retraction of said bolt moving to its second intermediate posia second retractible bolt for maintaining such intermediate position,

at portion to itsA roller subsequent to the retraction of said second position within the recess and. thereupon to a position on the second nat portion, and means acting on said plate to retract the -latter from the last named position to its first position and after the braking means has been rendered inoperative.

PIERRE GEORGES ALBERT LEVASSEUR. 

